An error occurred in the order of the reference list in this Education and Debate article by Bryan Williams et al (13 March, pp 634-40). Reference 8 in the published version (Williams et al) should have been reference 3; and the references published as 3 (Ramsay et al) to 7 (O'Brien et al) in the reference list should then have been renumbered and become references 4 to 8. The two references cited in the footnote to table 1 should be renumbered as 6 (European Society of Hypertension-European Society of Cardiology) and 7 (WHO-International Society of Hypertension); but the other references cited in the text of the article are correct. The pdf (but not the HTML) version on bmj.com has been amended.